Aromatic copolyestercarbonates have been known for many years. Their chief property improvement over polycarbonate is a higher distortion temperature under load, allowing it to be used in applications wherein higher temperature properties are required than standard polycarbonates. However, together with the higher temperature properties is the increased difficulty in molding. The melt viscosity is high, therefore requiring a higher temperature and/or more pressure to mold in comparison to the standard polycarbonates.
Various monofunctional groups have been employed to terminate polymers of the polycarbonate family. The standard endcapping monomers are phenol and paratertiary butylphenol. However, other endcapping agents have been disclosed from time to time. In U.S. Pat. No. 3,697,481, Bialous, et al assigned to General Electric Company, a chromanyl radical has been employed to endcap polycarbonates. The description of polycarbonates is broad enough to include copolyestercarbonates such as disclosed in U.S. Pat. No. 3,030,331 and U.S. Pat. No. 3,169,121, see the U.S. Pat. No. 3,697,481 at column 3, lines 59-69. In U.S. Pat. No. 4,238,596 issued to Quinn and assigned to General Electric Company, a new method for preparing copolyestercarbonates is disclosed. Following this new method, Examples 3 and 6 utilize chroman-I as a chain stopper. In Example 3, an aromatic copolyestercarbonate of 18 mole percent ester content is prepared utilizing 100 percent isophthalate units. In Example 6 an aromatic copolyestercarbonate is prepared having 11 percent ester content utilizing 100 percent terephthalate units.
It should be noted that in these cited references there is no general direction toward the paracumyl phenol endcapping substances but rather generally to the chromanyl endgroup utilizing Chroman-I as a specific example. The paracumyl phenol end group is a hydrocarbon except for, of course, the actual aromatic hydroxy linkage. Paracumyl phenol is a known endcapping agent for polycarbonates, see JP No. 57-133149. It is also known to use paracumylphenol as an endcapping agent for copolyestercarbonate having only terephthalate ester groupings and a limited total ester content, see U.S. Pat. No. 4,156,069 issued to Allied.
New chainstopped aromatic copolyestercarbonates have been discovered. These copolyestercarbonates endcapped with paracumyl phenol exhibit interesting processing and physical properties. While combining a high flow, low melt viscosity behavior with virtually undiminished physical properties of Notched Izod, as well as maintaining the impact resistance under heat and aging conditions, the paracumyl endcapped polymers show less color formation at low viscosity while retaining certain physical properties.